This invention relates to the use of certain prostaglandins in combination with certain growth factors to promote chondrocyte matrix or cartilage matrix production and thereby promote cartilage matrix synthesis and/or prevent the inhibition of cartilage matrix synthesis. In particular the invention relates to the use of a combination of prostaglandin, TGF-.beta. and/or IGF-1 to stimulate chondrocyte matrix or cartilage matrix production and thereby promote cartilage matrix synthesis and/or prevent the inhibition of cartilage matrix synthesis.